J Clin Pathol: first published as 10.1136/jcp.30.1.40 on 1 January 1977. Downloaded from J. clin. Path., 1977, 30, 40-44 Antibiotic-resistant Staphylococcus aureus in dermatology and burn wards G. A. J. AYLIFFE, WENDA GREEN, R. LIVINGSTON, AND E. J. L. LOWBURY From the Hospital Infection Research Laboratory and Bacteriology Department, Dudley Road Hospital and MRC Industrial Injuries and Burns Unit, Birmingham SUMMARY Staphylococcus aureus isolated between 1967 and 1975 from the nose and skin lesions of patients in dermatology wards and from the burns of patients in a burns unit in Birmingham showed a high incidence of multiple antibiotic-resistant strains in both environments. Over 20% of the strains isolated from patients on admission to the dermatology wards were multiresistant. Resistance to benzylpenicillin, tetracycline, erythromycin, and fusidic acid was common in the dermatology wards; a smaller proportion of strains were resistant to lincomycin, and few (since 1972 none) were resistant to methicillin; resistance to novobiocin and chloramphenicol was uncommon. In the burns unit, fusidic acid resistance was uncommon, but resistance to benzylpenicillin, tetracycline, ery- thromycin, novobiocin, neomycin, methicillin, and lincomycin was common. Several of the anti- biotics to which resistance was common in the burns unit were rarely if ever used there; strains resistant to these antibiotics probably remained common in the ward through the frequent use of other antibiotics, especially erythromycin, to which these strains were also resistant. copyright. Although infections caused by antibiotic-resistant all patients in three wards, and nose swabs were strains of Staphylococcus aureus are less of a taken from staff on duty. One survey was made in clinical problem than formerly, such organisms are 1967 and several surveys a year were made between still frequently isolated from septic operation 1970 and 1975. In February and March 1974, nose wounds, skin lesions, and burns. Some strains show and skin swabs were taken from 115 patients on resistance to most of the useful non-toxic antibiotics admission and on discharge from the dermatologicalhttp://jcp.bmj.com/ available (Ayliffe, 1973). These highly resistant wards. strains are often found in dermatological and burn In the Burns Unit of the Birmingham Accident wards, where cross-infection is common and where Hospital swabs moistened with peptone water were many patients are treated with topical and systemic used for sampling the burns of patients at change of antibiotics at some time during their long periods dressings and at operation, or daily in those treated of illness. Resistance to neomycin and fusidic acid by the exposure method. In addition, a series of has followed the topical use of these antibiotics 100 isolates of Staph. aureus was obtained from the on October 2, 2021 by guest. Protected (Lowbury et al., 1962, 1964; Alder and Gillespie, nares of patients attending the casualty department 1967; Smith et al., 1975). as examples of staphylococci in the community. In the present study, the results of surveys of staphylococcal carriage in dermatological wards BACTERIOLOGY METHODS in a Birmingham hospital and an investigation into In the dermatology wards Nose swabs were the possible origin of resistant strains in these wards cultured on nutrient agar containing phenolphthalein are reported; data are also presented on staphylo- diphosphate (Barber and Kuper, 1951) and 1 % cocci isolated from burns in the Birmingham Acci- serum; other swabs were cultured on blood agar dent Hospital during the same period of time. and McConkey medium. All plates were incubated for 18 hours, and presumptive Staph. aureus (phos- Methods phatase positive) was confirmed by slide or tube coagulase tests. Strains of Staph. aureus isolated In each survey at the Birmingham Skin Hospital from the surveys were tested for sensitivity to nose swabs and swabs from lesions were taken from antibiotics by the ditch-plate method. The ditches Received for publication 27 May 1976 contained benzylpenicillin, 10 units/ml; novobiocin, 40 J Clin Pathol: first published as 10.1136/jcp.30.1.40 on 1 January 1977. Downloaded from Antibiotic-resistant Staphylococcus aureus in dermatology and burn wards 41 Table 1 Antibiotic resistance of Staph. aureus isolatedfrom patients' noses in surveys ofdermatological wards, 1967-74 Antibiotic Percentage ofpatients carrying resistant strains 1967 1970 1971 1972 1973 1974 1975 Benzylpenicillin 20 37-8 49 41-4 42-1 40 8 47-3 Tetracycline 35 29-2 42-2 16 27-7 32-7 35-3 Erythromycin 17-5 10-9 26 5 10-9 22-6 22 32-7 Novobiocin 5 6 3-9 1-2 1-8 0 0-7 Chloramphenicol 0 3-6 1 0 0 1.1 0-7 Neomycin/kanamycin 10 11 13-7 4-2 10 23-9 28 Methicillin/cloxacillin - 1-2 2-9 0 0 0 0 Fusidic acid 2-5 8-5 21-6 8 13 8 12-1 20 Lincomycin/(clindamycin) - 0 15-7 4-6 7-5 4 6-7 Number of patients 40 82 102 237 159 272 150 - not tested lincomycin, fusidic acid, erythromycin, and methi- (corresponding to MICs of 8 to 128 jug/ml at 30°C). cillin, 10 ,ug/ml; streptomycin, tetracycline, chlor- In the year 1972, parallel tests made at 30°C and at amphenicol, and neomycin or kanamycin, 50 ,ug/ml. 37°C showed a close similarity of results when Plates for methicillin-resistance tests were incubated resistance was expressed in these terms. at 30°C. Staph. aureus isolated from the noses or lesions of patients on admission and discharge Results were tested by the disc method (Oxoid multi-disc) for sensitivity to the same antibiotics apart from DERMATOLOGY WARDS novobiocin and chloramphenicol. The minimum The antibiotic resistance of strains of Staph. aureus inhibitory concentration (MIC) of fusidic acid isolated from the noses of patients in the surveys is (Fucidin) and lincomycin for some strains was shown in Table 1. Carriage of strains resistant to copyright. determined by a tube dilution method. All strains penicillin, tetracycline, and, to a lesser extent, from surveys were phage typed with the routine set erythromycin and neomycin (kanamycin) occurred of phages kindly supplied by the Central Public throughout the period investigated. Strains resistant Health Laboratory, Colindale. to methicillin and chloramphenicol were isolated on a few occasions only. Strains resistant to fusidic In the Burns Unit Swabs were cultured on blood acid were first isolated in 1967 and to lincomycin 4% New Zealand and in in 1971. Strains resistant to both these antibiotics agar containing agar http://jcp.bmj.com/ cooked meat broth, which was subcultured after have remained in the wards, and strains of similar 48 hours' incubation to blood agar. Presumptive resistance were isolated from the skin lesions of Staph. aureus colonies were picked and confirmed many of the patients and from the noses of staff. by a tube coagulase test. The MICs for strains resistant to fusidic acid were The sensitivity of Staph. aureus to antibiotics was 8 to 16 ,ug/ml and for lincomycin-resistant strains tested by a ditch plate method similar to that > 128 ,ug/ml. In most instances the frequency of described above, but with 25 ,ug/ml methicillin and isolation of resistant strains was lower in 1972 than 10 ,ug/ml neomycin in the agar of the ditch for tests in previous years. This was apparently due to the on October 2, 2021 by guest. Protected of sensitivity to these antibiotics. In 1972, methi- closing of the wards for several weeks after a small cillin sensitivity tests were carried out on ditch outbreak of eczema vaccinatum in a few patients. plates incubated at both 30°C and 37°C. The same Since 1972 the incidence of resistant strains, par- strains were found to be fully sensitive (S) by both ticularly to fusidic acid and neomycin, has increased. methods, but a much larger proportion of strains were described as fully resistant (R) or moderately Antibiotic sensitivity patterns and phage patterns resistant ('R') in tests at 30°C than in those done at In 1967, the more resistant strains were usually of 37'C, and a much larger proportion were described phage group III patterns, eg, 6/47/53/54/75/77/83A as moderately sensitive ('S') in the test done at (Ayliffe, 1970). From 1970 to 1974 a wide range of 37°C. Methicillin resistance in 1972, 1973, 1974, antibiotic resistance patterns and phage types was and 1975 includes results shown as R and 'R' at obtained. These were mainly phage group III 30°C (corresponding, in parallel tube dilution patterns, often the same as in 1967. A selection of tests at 30°C, to MICs of 32 to 128 jug/ml and 16 to these strains is shown in Table 2. There appeared to 32 jug/ml respectively). In the earlier period, methi- be no correlation between antibiotic resistance cillin resistance is shown as R + 'R' + 'S' at 37°C patterns and phage types. J Clin Pathol: first published as 10.1136/jcp.30.1.40 on 1 January 1977. Downloaded from 42 G. A. J. Ayliffe, Wenda Green, R. Livingston, and E. J. L. Lowbury Table 2 Antibiotic resistance and phage patterns in available on the treatment given to most of the strains of Staph. aureus patients by general practitioners. Antibiotic resistance pattern' Phage pattern BURNS WARDS PTENLF 84/77 P T E N 6/47/53/54/77 Table 4 shows the proportion of strains of Staph. P T E N 84/85 aureus isolated from burns in the Birmingham P T E F 84/77/83A Burns Unit in the same years as those represented in P T E F L 84/54/77 TEFNoK 80 the study on dermatology wards.